Investments Schedule of Equity Securities (Details) - USD ($)	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Schedule of Equity Securities [Abstract]
Equity Securities at Fair Value	$ 916,900,000	$ 684,400,000
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Annual Amount	$ 200,000
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Cumulative Amount		$ 5.1

Schedule of Equity Securities [Abstract]

No definition available.

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- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

No definition available.

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- Definition

Amount of impairment loss on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117539-209714

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- Definition

Amount of cumulative impairment loss on investment in equity security without readily determinable fair value.

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